1. Field of the Invention
The present invention relates to a small-sized card device to be detachably inserted into a slot of an electronic apparatus and, particularly, to a wireless device wherein effects of diversity can be obtained even with a small size.
2. Description of the Related Art
In recent years, wireless devices such as card devices which include antennas and provide electronic apparatuses with wireless communications functions have been widely used. Card devices of this type are typified by wireless LAN cards and card-type modems. In addition, card devices for the addition of wireless communications functions also provide additional system resources such as memories.
In addition, wireless devices of this type include devices that have a plurality of antennas and in that antenna diversity has been realized. Satisfactory communications conditions are easily obtained when antenna diversity relieves harmful influences due to phasing.
In further detail, a space diversity scheme is used, wherein two or more antennas are arranged so as to be physically separated and one of the antennas with the superior communications condition is selected. Namely, a contrivance has been made so that, by separating the antenna positions, the antennas are not electrically coupled to each other and the individual antennas have unique radiation characteristics.
Smaller and lighter wireless devices have been demanded for wireless devices of this type. For example, when a radio wave having a 2.4 GHz band is used, it is possible to mount two antennas on wireless devices as long as they approximate the size of a Personal Computer Memory Card International Association (PCMCIA) card.
However, if the device becomes smaller than this size, e.g., for reasons concerning space, it is difficult to mount two antennas in a separate fashion, and in most cases, only one antenna can be mounted. In these cases, no space diversity effects are obtained.
In regard hereto, wireless devices having small-sized chips as antennas have been put into market circulation, however, even if such small-sized antennas are used, problems similar to the foregoing exist.